Species-specific ingestion of organic carbon by deep-sea benthic foraminifera and meiobenthos: In situ tracer experiments

We measured organic carbon uptake rates by deep-sea benthic foraminifera and studied differences among species, living depth, and seasons to investigate how these protists contribute to carbon consumption on the deep-sea floor. In situ feeding experiments using C-13-labeled algae were carried out in the central part of Sagami Bay from 24 to 29 November 2001 and 1 to 12 April 2002. Our results indicate that carbon assimilation rates were higher in shallow infaunal species (Uvigerina akitaensis, Bulimina aculeata) and lower in intermediate (Textularia kattegatensis) and deep infaunal species (Chilostomella ovoidea). Some shallow and intermediate infaunal species showed higher carbon uptake in spring than in autumn. In total, benthic foraminifera assimilated C at 5.8 +/- 4.8 mg m(-2) and 2.0 +/- 1.3 mg m(-2) (in spring and in autumn, respectively) of labeled algae within 2 d, which was more than that by total metazoans (1.5 +/- 0.4 mg m(-2) and 0.4 +/- 0.1 mg m(-2), respectively). Deep-sea benthic foraminifera rapidly ingest large amounts of carbon and may play an important role in carbon consumption on the deep-sea floor. Different responses to algal carbon among species may explain foraminiferal assemblages and shifts after environmental changes, such as seasonal pulses of organic matter supply.